A toll-free number is a telephone number in which the cost of the call is charged to the called party rather than to the calling party. In countries that follow the North American Numbering Plan (NANP), telephone numbers are of the form NPA-NXX-YYYY, where NPA is the numbering plan area code, roughly corresponding to a particular geographical area, and NXX is the exchange, which identifies a physical switching facility, called a central office (CO). The remaining digits, YYYY, identify a line card within the CO. When a CO detects that a subscriber whom that CO serves is attempting to place a call to called party telephone number, the values of NPA and NXX of the called party number are used by a switch to determine how to route a call.
A toll-free number, however, may have an “8XX” area code (e.g., 800, 877, 866, etc.), that does not correspond to any geographical location of the called party, and thus cannot be used by itself to determine the destination of the call or how it should be routed. For this reason, switches in conventional telecommunications networks that provide toll free service must send a query to a toll-free database to determine the true destination of the toll-free called party. For example, a CO in a signaling system number 7 (SS7) network may issue a transaction capabilities application part (TCAP) query to a service control point (SCP) that maintains a toll-free database. A query to a toll-free database is herein referred to as a “toll-free query.”
Thus, in conventional telecommunications networks, toll-free (TF) service is provided by the switch, which issues a toll-free query in response to detecting an attempt to place a call to a toll-free called party. In these conventional implementations, the switch must be configured or provisioned to perform the additional steps needed to provide toll-free service. For example, when the switch detects a call attempt, the switch must additionally determine whether the called party is a toll-free number, and if so, issue a toll-free query to a toll-free database that maps the toll-free number to a directory number (DN), and receive the DN associated with the toll-free number. The switch can then route the call setup message accordingly.
In telecommunications networks that support number portability (NP), a subscriber may change location and/or service provider but still keep the same directory number. In this scenario, a subscriber may have been moved from the original switch that served the subscriber, called the donor switch, to a new switch, called the recipient switch. Thus, in telecommunications networks that support number portability, the switch must be additionally configured to perform a NP lookup using the first DN, i.e., the DN that was returned by the toll-free query. If the directory number associated with the toll-free number has been ported, the NP query may return a second DN, a routing number (RN) of the recipient switch, or both.
A telecommunications network may support wireline subscribers, wireless subscribers, or both. A “wireline subscriber” is a subscriber to or user of a network who accesses the network over a physical connection, such as a telephone line, local loop, cable modem, or other physical medium including wire or optical fiber. A “wireless subscriber” is a subscriber to or user of a network who accesses the network over a wireless connection, such as via a mobile phone, wireless LAN, wireless modem, etc. A wireless subscriber may also be referred to as a “mobile subscriber”.
If the telecommunications network supports mobile subscribers, the switch must also be configured to perform a mobility management query using available information, e.g., the first DN, the second DN, or the RN. A mobility management query may return information identifying the mobile switching center that is currently serving the mobile subscriber.
There are disadvantages associated with the conventional system described above. Providing toll-free service at a switch requires that the switch be configured to perform at least one query—the toll-free query—and possibly additional queries, such as the NP query and mobility management query, which further requires the switch to maintain and support more complicated call state machines.
These additional features or capabilities may increase the cost of each switch, and this additional cost may increase in proportion to the number of switches in the telecommunications network. In addition to the direct costs associated with the additional configuration and provisioning, there is the potential for increased indirect costs associated with the additional time required to provision or update each switch. As the complexity of each switch increases, maintenance and repair may become more difficult and therefore more time consuming and costly as well. In short, configuring all of the switches in a telecommunications network to support additional protocols increases the complexity of the network and may increase the costs of deployment and maintenance of that network.
Accordingly, in light of these disadvantages associated with conventional approaches to providing toll-free service in a telecommunications network, there exists a need for improved systems and methods for providing toll-free service in a telecommunications network.